The invention relates to gun sight reticles, and in particular to gun sight reticles that provide for bullet drop compensation.
It is common to use a gun sight, in particular, a telescopic gun sight (also called a “scope”), for longer-range guns such as rifles and for shorter-range guns such as muzzle-loaders and shotguns. With either type of gun, the projectile follows a generally parabolic trajectory. The particular trajectory depends upon both the gun and the projectile. An experienced shooter knows that one must consider the projectile trajectory and distance to target when aiming at the target. Depending upon the distance to the target, one might need to aim over the target so that the projectile strikes the target where intended.
In order to assist shooters, it is known to provide gun sights having aiming points (also called “sighting marks”) in addition to the central aiming point formed by a center horizontal hairline and a center vertical hairline that forms an aiming point at the center of a reticle. These conventional reticles, known as bullet drop compensation reticles, typically have a plurality of aiming points formed by a plurality of intersecting hairlines located at predetermined distances below the central aiming point. These bullet drop compensation reticles provide additional horizontal hairlines at specified distances below the center horizontal hairline so as to form the additional aiming points where those additional horizontal hairlines intersect the center vertical hairline. See, for example, U.S. Pat. No. 5,920,995 and U.S. Pat. No. 6,591,537. The disclosures of U.S. Pat. No. 5,920,995 and U.S. Pat. No. 6,591,537 are hereby incorporated herein by reference in their entireties.
U.S. Pat. No. 7,171,775, entitled “Gun Sight Reticle Having Open Sighting Areas for Bullet Drop Compensation” discloses a reticle in which the bullet drop compensation aiming points are defined by open areas, for example, circular areas circumscribed by indicia. The open sighting areas are advantageous because there is no indicia (markings) at the aiming point, and thus the shooter has a better view of the target. The open sighting areas are disposed at fixed positions below the central aiming point as are the crosshair-type bullet drop compensation aiming points of the two patents identified above. The disclosure of U.S. Pat. No. 7,171,775 is incorporated herein by reference in its entirety.
Prior to using a gun having a scope fitted with a bullet drop compensation reticle, the shooter typically adjusts the scope. In particular, the scope includes adjustment mechanisms for adjusting the vertical and horizontal position of the scope, and those mechanisms are adjusted so that a projectile fired by the gun will strike a target at a known distance (for example, 100 yards or 200 yards) when the central aiming point of the reticle is aligned with that target. This process can be considered to be a “calibration” process. The bullet drop compensation aiming points are disposed at fixed positions vertically below the central aiming point. For example, a first bullet drop compensation (BDC) aiming point is located a first predetermined distance directly below the central aiming point, a second BDC aiming point is located a second predetermined distance (greater than the first predetermined distance) below the central aiming point such that the second BDC aiming point is directly below the first BDC aiming point, etc. Thus, after the scope is calibrated, the shooter can position the first BDC aiming point on a target that is a first distance (for example, 300 yards) from the shooter, position the second BDC aiming point over a target that is a second, greater distance (for example, 400 yards) from the shooter, etc.